The Spanish veteran has scored regularly for the Hong Kong First Division champions, including 10 times in the Asian tournament.
Belencoso, 33, had spent several seasons in his homeland before making the move abroad, and he has impressed.
Jose Francisco Molina will be looking to the forward to lead the way at the Prince Mohammed Stadium in Jordan, where Iraq's Erbil are hosting.
Molina, who was a goalkeeper for Spain, Atletico Madrid and Deportivo La Coruna, is Villarreal's former coach.
Kitchee crushed Wofoo Tai Po 4-1 in their league opener on Friday.
They have a huge chance to reach their maiden AFC Cup final, while Erbil were runners-up in 2012.
Iraq international Amjad Radhi scored twice in Erbil's 3-0 aggregate win over Ha Noi T&T in the quarter-finals and he could make the difference in the last four tie.
